Volcanoes and Plate Tectonics

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Vocabulary

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Volcano: a weak spot on our planet's surface where molten material, or magma, comes to the crust
Magma: a molten mixture of rock-forming substances, gases, and water from the mantle
Lava: liquid magma that reaches the surface; also the rock formed when liquid lava hardens
Ring of Fire: a major belt of volcanoes that rims the Pacific Ocean
Island Arc: a string of islands formed by the volcanoes along a deep ocean trench
Hot Spot: an area where magma from deep within the mantle melts through the crust above it

Outline

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What is a Volcano ?

• Magma comes to the surface, when it reaches the surface it's called magma
  • After lava cools it turns into solid rock
    • The lava released builds up Earth's surface

Location of Volcanoes

• one major volcano belt is the Ring of Fire
  • most volcano belts form along plate boundaries
    • At plate boundaries, huge pieces of the crust diverge ( pull apart) or converge (push together)
      • hear the crust is too weak that the magma can easily get through

Volcanoes at Diverging Plate Boundaries

• volcanoes form along the mid-ocean ridge
  • along the ridge lava pours out of cracks into the ocean floor
    • In very few places like, Iceland and Azores Islands in the Atlantic Ocean, the volcanoes of the mid-ocean ridge rise above the ocean's surface

Volcanoes at Converging Boundaries

• many volcanoes occur on islands or near boundaries where two oceanic plates collide
  • the older, denser plate dives under the other plate creating a Deep-ocean trench

Hot Spot Volcanoes

• hot spots often lie in the middle of Continental or oceanic plates for from any plate boundaries
  • Hot spots can also form under continents
    • There is a major hot spot under the North American Plate at Yellowstone National Park in Wyomin

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